iv MENTAL DEVELOPMENT 49 



by the structure represents, therefore, the sum of all 

 previous adaptations of a successful kind. 



(2) Reflex Action. 



But life cannot depend on internal forces alone. The 

 organism is constantly meeting changes in the environment, 

 and it must be somehow fitted to deal with these or it will 

 perish. The structure must respond to changes as to a 

 stimulus, and the response must be one normally suited to 

 the requirements of the organism in relation to the stimulus. 



The most elementary form of such response is known 

 as a Reflex act. It is one in which the stimulus of an 

 external object calls forth a uniform response on the part 

 of an organic structure. 1 Thus the touch of something 

 sharp or hot sets up muscular contractions or results in the 

 withdrawal of the limb. The contact of a crumb with the 

 windpipe induces a cough, a touch on the pseudopodium 

 or limb of protoplasm which a rhizopod puts forth causes 

 it to shrink up and withdraw. Normally the reflex act 

 serves a perfectly intelligible function in the life of the 

 organism thus in all the instances given it helps to 

 protect from possible injury. But though it serves this 

 function it would be mistaken to infer that it is performed 

 because it serves it. This would be true at best only in 

 a very roundabout sense which we shall presently consider. 

 We have first to note that the precise differentia of the 

 reflex is its unintelligent and quasi-mechanical character. 



To begin with, consciousness plays no essential part in 

 it. I am conscious of sneezing, but the consciousness is 

 here a mere effect, and the sneeze carries itself out auto- 

 matically and even against my will. I blink without 

 knowing it, and cannot help blinking even when I know 

 that there is no danger to my eyes. The reflex may even 

 be injurious, for it is adapted only to the normal, and yet 

 it may be difficult or impossible to control it, and so the 



1 The reflex may be inhibited or modified by other parts of the 

 organic structure. But as long as we have evidence that the tendency 

 to react belongs to the structure as such in relation to the stimulus as 

 such we can call the response a reflex. V. Sherrington, The Integrative 

 Action of the 'Nervous System, p. 7 seej. 



D 



